1. Field of the Invention
The present invention relates generally to cutting tools and more specifically to a non-adjustable single cylindrical lip boring tool which allows a machinist to greatly reduce the amount of time needed to create accurately located dowel pin holes in a piece part.
2. Discussion of the Prior Art
A problem frequently encountered with machine tools such as vertically spindled milling machines is maintaining locational accuracy of reamed dowel pin holes in a metal piece part. A dowel pin hole is commonly created by first drilling an undersized hole. The problem with the undersized hole is that drills tend to stray away or walk from the intended location, even when a center drill is employed. One way to solve the drill runout problem is to use a boring bar to straighten out the drill hole. The boring bar creates an opening which is a few thousands smaller than a reamer. The reamer is then used to remove the remaining few thousands of material. If the reamer were used without a boring bar, the reamer would follow the runout in the drilled hole and produce an inaccurately located dowel pin hole. Unfortunately, setting up the boring bar for creating the dowel pin hole is very time consuming. The drawback to using a boring bar is that the boring bar must be adjusted often as the bored hole is increased to the desired few thousands under reamer size.
Another solution to the problem of drill hole runout is to use an undersized end mill. The undersized end mill has the rigidity to prevent being pulled into a run out situation by a drill hole with runout. The drawback of the undersized end mill is two fold. First, end mills are not manufactured undersize. The supply for undersized end mills comes from worn end mills that have had their diameters resharpened. The other problem is that the end mill diameter may be inaccurately ground to a slightly negative taper along its axial length; this may cause one flute of the end mill to grab the side wall of the hole and lose hole locational accuracy.
Accordingly, there is a clearly felt need in the art for a non-adjustable single cylindrical lip boring tool which allows a user to consistently create an accurately located straight hole for final reaming of a dowel pin hole without time consuming boring bar set-up.